Fiber-reinforced polymer composites are high-performance structural materials that are composed of a resin matrix and reinforcement fibers. These fiber-reinforced polymer composites have been used for fabricating structural parts that require high strength, and/or low weight, and resistance to aggressive environments. Examples of such structural parts include aircraft components (e.g. tails, wings, fuselages, propellers). The fibers reinforce the matrix resin, bearing the majority of the load supported by the composite, while the resin matrix bears a minority portion of the load supported by the composite and also transfers load from broken fibers to intact fibers. In this manner, these polymeric composites may support greater loads than either the matrix resin or fibers may support alone. Furthermore, by tailoring the reinforcing fibers in a particular geometry or orientation, the composite can be efficiently designed to minimize weight and volume.
Fiber-reinforced polymer composites are traditionally made from sheets of resin-impregnated fibers, also known as prepregs. To form a composite part from the prepregs, a plurality of prepreg layers may be laid up within a mold, and heat may be applied to cause the matrix resin to flow, enabling consolidation of the prepreg layers. The applied heat may additionally cure or polymerize the matrix component.
The consolidation of prepregs to form composites in this manner presents problems, however. Gases such as air may be trapped inside the individual prepreg and between the prepreg layers during layup. Furthermore, volatiles may also evolve during heating and/or curing of the prepregs. These gases are difficult to remove from the layup, as the matrix substantially inhibits movement of the gases and may result in porosity within the final, cured composite. Porosity refers to the voids within the cured composite material. This porosity could further negatively affect the mechanical properties of the final, cured composite.
Techniques have been developed to enhance removal of entrapped gases during composite fabrication, however, problems remain. For example, edge breathers may be employed to apply vacuum to the edge of prepregs in order to draw out gases from the sides of prepreg layers. However, removal of trapped gases from prepregs in this manner is slow and may not substantially remove all of the trapped gases.